Plants annual or perennial, sometimes with
rhizomes and/or tuberous thickenings, monoecious or with perfect flowers.
Aerial stems circular in cross-section or often 3-angled. Leaves basal and/or
alternate, often noticeably 3-ranked, grasslike, parallel-veined, the bases
strongly sheathing, the sheaths almost always closed (fused around the stem all
or most of the way to the summit), sometimes with a ligule on the inner (upper)
surface at the tip, the leaf blades sometimes lacking or highly reduced. Basic
units of inflorescences spikelets or spikes (see discussion in
the introductory portion of the Carex treatment), these 1 to many,
terminal and/or axillary (sometimes basal), arranged into panicles, headlike clusters,
or umbels that are often subtended by 1 or more leaflike (or less commonly
stemlike or scalelike) bracts. Individual flowers (florets) of a
spikelet or spike subtended by scalelike bracts (referred to as scales
by most botanists and in this treatment). Perianth absent or reduced to 1–6
(rarely more) bristles or small scales attached below the ovary. Stamens 1–3.
Pistil 1, naked or enclosed in a saclike perigynium in Carex. Style 1,
branched into 2–3 stigmas at the tip, sometimes persistent at the tip of the
fruit as a beak of the same color and texture as the fruit, or as a conical or
triangular tubercle that differs in texture and/or color from the main body of
the fruit and is separated from it by a line or constriction. Ovule 1 per
floret. Fruits achenes. Eighty to 115 genera, 3,500–4,500 species, worldwide.

The Cyperaceae are a large and
taxonomically difficult family that still requires detailed taxonomic study on
a worldwide basis. Generic limits for many of the groups are hotly debated by
specialists, which has resulted in a confusing array of generic transfers in
the literature, and often markedly different treatments of the same species
groups in floristic manuals covering regions in North America, Europe, Africa, and elsewhere. The treatment below generally follows the generic classification of
Bruhl (1995) and accepts many of the recent generic reassessments. However, Cyperus
is treated in the relatively broad, traditional fashion (see the treatment of Cyperus
for further discussion).

Determination of genus and species for a
specimen in this family requires patience and detailed observations using a
hand lens or dissecting microscope. Collectors should note that rootstocks and
mature fruits usually are necessary for accurate determinations. Vegetative or
flowering plants of Cyperaceae generally should be avoided. In a few cases,
determinations are aided by observation of both fertile and vegetative shoots
and their respective leaf arrangements.

The determination of annual vs. perennial
growth form is important for keying plants of most genera of Cyperaceae, but
this can be difficult to establish for some plants. In general, annual species
have “soft bases” that can usually be pulled from the ground with their roots
relatively intact and show no evidence of rhizomes, tuberous root thickenings,
or previous years’ stem or leaf bases. Perennials have “hard bases” that are
frequently (but not always) difficult to pull up with intact rootstocks, often
have rhizomes, tuberous roots, or otherwise thickened rootstocks, and usually
have remnants of previous years’ stem and/or leaf bases.

Florets all or mostly perfect, sometimes the apical or basal ones of a spikelet staminate, the scales all alike or not differentiated into 2 kinds; fruits rarely white, not appearing hard and bony at maturity, if rarely white then with a tubercle at the tip

Spikelets with 3 to many alternating scales (2 somewhat reduced scales also at the spikelet base), the fertile florets 2 to many, or if reduced to 1 then the inflorescence noticeably branched, the spikes with short to long stalks

Spikelets with 2 more or less opposite scales (1–2 highly reduced scales usually visible with magnification at the spikelet base), the fertile floret 1; inflorescence of 1–3 headlike spikes, these short, sessile, dense

Style bases not enlarged, or if thickened then either not persisting on the mature fruit as a tubercle or the fruit tapered to a persistent beak that is not differentiated in texture or color from the main body of the fruit

Ovaries and fruits subtended by 1–6 (rarely more) scales and/or bristles (do not confuse bristles with the smooth, flattened filaments of the stamens, which can persist after the anthers have dropped off; the bristles generally have a different texture from the filaments and are often barbed)